A former Diablo View Middle School student has filed a lawsuit against the Mt. Diablo school district, the school's principal and a teacher who was convicted last year of having sex with her while she was a minor.

The now 18-year-old woman living in Contra Costa County is seeking at least $25,000 in damages. She alleges in a lawsuit filed Monday in Contra Costa Superior Court that sexual activity and other acts between herself and former middle school math and science teacher Andrew Cottrell caused her emotional distress and physical and psychological injuries. She filed the lawsuit as "Jane Doe."

The girl's parents found out about the relationship in December 2011 and notified police, leading to Cottrell's arrest and conviction on multiple felony charges. He was sentenced last June to nine years in prison.

The abuse could have been prevented if Principal Patti Bannister and other district officials had investigated previous complaints and properly supervised the sixth-grade teacher, the lawsuit filed by Santa Cruz attorney David Fulton alleges.

Bannister said Wednesday that she was unaware of the lawsuit. She denied any knowledge of prior complaints.

"Since this is the very first I've heard of this," she said, "I'm not going to make any comment."

General Counsel Greg Rolen declined to comment, saying the district had not yet been served with the complaint, and he was not aware of any prior claim filed against the district.

Fulton could not be reached for comment. His court filing states that Cottrell began "grooming" the girl when she was an 11-year-old student, portraying himself as a "cool" teacher.

When she entered seventh grade, Cottrell kept the girl after school to clean his classroom, the lawsuit says. In eighth grade, she was his teacher's assistant during prep period, with no other students present. Cottrell began flirting with the girl and shared personal information, communicating with her via email, loaning her CDs and giving her gifts, according to the lawsuit.

When the girl started high school, Cottrell asked her to baby-sit for his children and expressed feelings for her in emails, court documents state. The relationship became sexual, including encounters in Cottrell's middle school classroom closet, according to the lawsuit.